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ENGRAM Protocol — Local Disk Storage Backend
Directory layout:
{data_dir}/{model_family}/{agent_id}/{date}/{cache_id}.eng
Phase 1 production backend. Zero infrastructure dependencies.
Uses safetensors header-only read for metadata operations.
D7: One safetensors file per 256-token block.
"""
from __future__ import annotations
import logging
import shutil
from collections import defaultdict
from datetime import datetime, timezone
from pathlib import Path
logger = logging.getLogger(__name__)
from kvcos.core.serializer import EngramSerializer
from kvcos.core.types import ENG_FILE_EXTENSION, CacheStats, EngramMetadata
from kvcos.storage.backends import StorageBackend
class LocalStorageBackend(StorageBackend):
"""Local filesystem storage for .eng files.
Files organized by model family, agent ID, and date.
"""
def __init__(self, data_dir: Path):
self.data_dir = data_dir
self.data_dir.mkdir(parents=True, exist_ok=True)
self._serializer = EngramSerializer()
self._index: dict[str, Path] = {} # cache_id → file path
self._rebuild_index()
def _rebuild_index(self) -> None:
"""Scan data directory and rebuild in-memory path index."""
self._index.clear()
for eng_file in self.data_dir.rglob(f"*{ENG_FILE_EXTENSION}"):
cache_id = eng_file.stem
try:
meta = self._serializer.read_metadata_only(eng_file)
if "cache_id" in meta:
cache_id = meta["cache_id"]
except Exception as e:
logger.debug("Skipping metadata for %s: %s", eng_file.name, e)
self._index[cache_id] = eng_file
def _resolve_path(self, metadata: EngramMetadata) -> Path:
"""Determine storage path from metadata."""
model_family = metadata.get("model_family", "unknown")
agent_id = metadata.get("agent_id", "default")
date_str = datetime.now(timezone.utc).strftime("%Y-%m-%d")
cache_id = metadata.get("cache_id", "unknown")
path = self.data_dir / model_family / agent_id / date_str / f"{cache_id}{ENG_FILE_EXTENSION}"
path.parent.mkdir(parents=True, exist_ok=True)
return path
def store(self, cache_id: str, data: bytes, metadata: EngramMetadata) -> str:
metadata_copy = dict(metadata)
metadata_copy["cache_id"] = cache_id
path = self._resolve_path(metadata_copy) # type: ignore[arg-type]
tmp_path = path.with_suffix(f"{ENG_FILE_EXTENSION}.tmp")
try:
tmp_path.write_bytes(data)
tmp_path.rename(path)
except Exception:
tmp_path.unlink(missing_ok=True)
raise
self._index[cache_id] = path
return str(path)
def store_file(self, cache_id: str, source_path: Path, metadata: EngramMetadata) -> str:
metadata_copy = dict(metadata)
metadata_copy["cache_id"] = cache_id
dest_path = self._resolve_path(metadata_copy) # type: ignore[arg-type]
if source_path == dest_path:
self._index[cache_id] = dest_path
return str(dest_path)
tmp_path = dest_path.with_suffix(f"{ENG_FILE_EXTENSION}.tmp")
try:
shutil.copy2(str(source_path), str(tmp_path))
tmp_path.rename(dest_path)
except Exception:
tmp_path.unlink(missing_ok=True)
raise
self._index[cache_id] = dest_path
return str(dest_path)
def get(self, cache_id: str) -> bytes | None:
path = self._index.get(cache_id)
if path is None or not path.exists():
return None
return path.read_bytes()
def get_path(self, cache_id: str) -> Path | None:
path = self._index.get(cache_id)
if path is None or not path.exists():
return None
return path
def get_metadata(self, cache_id: str) -> EngramMetadata | None:
path = self._index.get(cache_id)
if path is None or not path.exists():
return None
try:
return self._serializer.read_metadata_only(path)
except Exception as e:
logger.warning("Failed to read metadata for %s: %s", cache_id, e)
return None
def delete(self, cache_id: str) -> bool:
path = self._index.pop(cache_id, None)
if path is None or not path.exists():
return False
path.unlink()
parent = path.parent
try:
while parent != self.data_dir:
if not any(parent.iterdir()):
parent.rmdir()
parent = parent.parent
else:
break
except OSError:
pass
return True
def list_entries(
self,
agent_id: str | None = None,
model_family: str | None = None,
limit: int = 100,
) -> list[EngramMetadata]:
results: list[EngramMetadata] = []
for cache_id, path in self._index.items():
if len(results) >= limit:
break
if not path.exists():
continue
try:
meta = self._serializer.read_metadata_only(path)
except Exception as e:
logger.debug("Skipping %s in list_entries: %s", cache_id, e)
continue
if agent_id and meta.get("agent_id") != agent_id:
continue
if model_family and meta.get("model_family") != model_family:
continue
results.append(meta)
results.sort(key=lambda m: m.get("created_at", ""), reverse=True)
return results[:limit]
def exists(self, cache_id: str) -> bool:
path = self._index.get(cache_id)
return path is not None and path.exists()
def stats(self) -> CacheStats:
total_entries = 0
total_size = 0
model_counts: dict[str, int] = defaultdict(int)
for cache_id, path in self._index.items():
if not path.exists():
continue
total_entries += 1
total_size += path.stat().st_size
try:
meta = self._serializer.read_metadata_only(path)
model_counts[meta.get("model_family", "unknown")] += 1
except Exception as e:
logger.debug("Metadata read failed for %s: %s", cache_id, e)
model_counts["unknown"] += 1
return CacheStats(
total_entries=total_entries,
total_size_bytes=total_size,
avg_compression_ratio=0.0,
model_breakdown=dict(model_counts),
)
def vacuum(self) -> int:
"""Remove stale index entries for deleted files."""
stale = [cid for cid, path in self._index.items() if not path.exists()]
for cid in stale:
del self._index[cid]
return len(stale)
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